Project Mercury astronauts practise movement in zero gravity onboard a US Air Force plane. The plane creates a weightless environment by flying in a parabolic curve. Project Mercury was the first human spaceflight programme of the United States. It ran from 1959 to 1963, succeeding in putting the first US astronaut in space on 5 May 1961. A total of six manned Mercury missions were flown. The Mercury astronauts were Alan B. Shepard, Walter M. Schirra, John H. Glenn, Virgil I. Grissom, M. Scott Carpenter, Donald Slayton, and L. Gordon Cooper.